1. Field of the Invention
The present invention relates to a novel semicarbazide/urethane mixture which is useful as a stabilizer for polyurethane. More particularly, the invention concerns such a stabilizer which is derived from 4-amino-1,2,4-triazole, an aliphatic polyisocyanate and a reduced sugar or glycerol and is particularly useful as a stabilizer for spandex.
2. Description of the Prior Art
Polyurethanes derived from polyethers or polyesters, especially those intended for use in spandex, require protection against discoloration caused by oxidation, atmospheric fumes, nitrogen oxide gases, exposure to light, and the like. Many stabilizers have been disclosed for use in these polymers. For example, U.S. Pat. No. 3,399,167, Rosendahl et al, discloses 1,1-dialkyl-semicarbazides and 1,1-dialkyl-carbazinic acid esters as stabilizers for polyurethanes. Most of the many semicarbazides disclosed by Rosendahl et al, are derived from asymmetrically substituted dialkyl hydrazines; only one is derived from a triazole, namely the bis-semicarbazide of the reaction of 4-amino-1,2,4-triazole and hexamethylene diisocyanate. However, the present inventors found that this semicarbazide compound is only sparingly soluble in solvents usually employed for dry spinning spandex and therefore is not practically usable for producing spandex.
U.S. Pat. No. 4,973,618, Ultee discloses protecting spandex from discoloration by atmospheric fumes and/or light, with oligomeric additives of 1,000 to 5,000 molecular weight, prepared from polyether glycols, diisocyanates and 1,1-dialkylhydrazines. These oligomers avoid problems of additive extraction during scrubbing, washing and like operations, as was commonly encountered with previously known semicarbazide additives.
Generally, the stabilizers disclosed by Ultee and by Rosendahl et al (except for the bis-semicarbazide derived from 4-amino-1,2,4-triazole) require unsymmetrical dialkylhydrazines for their manufacture. However, unsymmetrical dialkylhydrazines are highly toxic, and the 1,1-dimethylhydrazine, the most commonly used dialkylhydrazine is a flammable, carcinogenic compound that oxidizes to dimethyl nitrosamine, which is an even more powerful carcinogen.
U.S. Pat. No. 5,028,642, Goodrich et al, discloses improved spandex containing zinc oxide and a polyhydroxy additive selected from certain sugars, reduced sugars and/or polyhydroxy urethanes formed from the sugars or reduced sugars and an organic diisocyanate.
The objects of the present invention are to provide a stabilizer for spandex that (a) is soluble in solvents commonly used for dry-spinning spandex, (b) does not require handling of hazardous unsymmetrical substituted dialkylhydrazines and (c) does not require zinc oxide in its formulation.